This invention relates to shuttle cleaning of heat exchanger tubes and is an improvement over the concepts disclosed in the above-identified patents.
It is known from U.S. Pat. Nos. 3,319,710 and 4,124,065 to connect individual elongated cleaning element capturing cages or baskets to both ends of longitudinally extending tubes disposed in a heat exchanger housing. The tube ends are held in position at both ends by transverse tube sheets. The baskets are adapted to contain shuttlable cleaning elements, such as brushes. Fluid flowing in one direction through the tubes keeps the cleaning elements captured within their respective basket chambers, while the fluid discharges outwardly through slot-like openings in the basket walls. Upon reversal of fluid flow, the cleaning elements are forced out of their baskets and through the tubes to the baskets at the opposite tube ends to thereby perform a tube cleaning action.
In low temperature applications, brushes and baskets are often made of plastic materials. In high temperature situations, such as in the cracking of crude oil, plastic may not be suitable and metal elements may be needed.
Broadly, it is known to use coiled metal springs as cleaning elements for pipe lines. See, for example, U.S. Pat. Nos. 3,460,180 and 3,474,479. In addition, it is known from these two patents to provide a coiled metal cleaning element having members on each end which sealingly engage the pipe walls. It is also known to mount a cleaning element on a central shaft, such as in U.S. Pat. Nos. 2,506,530 and 3,484,886.
It is a task of the present invention to provide an improved cleaning arrangement for heat exchanger tubing wherein a shuttling tube cleaning means is utilized which is automatically self-cleaning adjacent both ends of the tube.
It is a further task of the invention to utilize the forces of inertia to assist in removing built up undesirable material on the shuttlable cleaning element.
It is another task of the invention to provide a spring tube cleaning means which is free along its entire length to move transversely of the pipe during shuttling to improve the cleaning action.
In accordance with the various aspects of the invention, a shuttle assembly is provided which includes a spring cleaning element secured at each end to mounting members which are freely slideable on a longitudinal axial rod. The rod is longer than the cleaning element in its normal extended position so that the cleaning element can shuttle back and forth on the rod. Stop members are secured to the end portions of the rod. When either rod end engages a capturing device at the end of a heat exchanger tube, inertia causes the cleaning element to slide forwardly until the adjacent mounting member tappingly engages the adjacent stop member of the assembly, causing undesirable material on the cleaning element to drop off.
The mounting members are of a lesser O.D. (Outside Diameter) than the I.D. (Inside Diameter) of the pipe to permit fluid to pass through the assembly during shuttling. The mounting members are also of a lesser O.D. than the O.D. of the normally extended cleaning element.
The O.D. of the cleaning element is such as to allow for transverse rattling engagement with the inner tube wall during shuttling.